Add MockController to mock http-400

AsbCloudWebApi/Controllers/BackgroundWorkController.cs

@@ -33,8 +33,11 @@ namespace AsbCloudWebApi.Controllers
         [HttpGet("Current")]
         public IActionResult GetCurrent()
         {
-            var result = (BackgroundWorkDto?)backgroundWorker.CurrentWork;
-            return Ok(result);
+            var work = backgroundWorker.CurrentWork;
+            if (work == null)
+                return NoContent();
+
+            return Ok(work);
         }
 
         [HttpGet("Failed")]

AsbCloudWebApi/Controllers/Mock.cs

@@ -0,0 +1,42 @@
+using Microsoft.AspNetCore.Mvc;
+using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
+using System.Linq;
+
+namespace AsbCloudWebApi.Controllers
+{
+    [Route("api/[controller]")]
+    [ApiController]
+    public class MockController : ControllerBase
+    {
+        /// <summary>
+        /// получить статистику  
+        /// </summary>
+        [HttpGet("400")]
+        [ProducesResponseType(typeof(ValidationProblemDetails), (int)System.Net.HttpStatusCode.BadRequest)]
+        public IActionResult Get([FromQuery, Required]IDictionary<string, string> args)
+        {
+            var errors = new Dictionary<string, string[]>();
+            
+            foreach (var arg in args)
+            {
+                var countOfErrors = ((arg.Key + arg.Value).Length % 3) + 1;
+                var errorsText = Enumerable.Range(0, countOfErrors)
+                    .Select(i => $"{arg.Value} не соответствует критериям проверки № {i}");
+
+                errors.Add(arg.Key, errorsText.ToArray());                
+            }
+
+            if (errors.Any())
+            {
+                var problem = new ValidationProblemDetails(errors);                
+                return BadRequest(problem);
+            }
+            else
+            {
+                var problem = new ValidationProblemDetails { Detail = "at least one argument must be provided" };
+                return BadRequest(problem);
+            }
+        }
+    }
+}